1. Field of the Invention
The present invention relates to an ophthalmic apparatus used for ophthalmoscopy and tonometry at ophthalmic hospitals and the like.
2. Related Background Art
The ophthalmic apparatus conventionally known includes the ophthalmic apparatus arranged to carry out automatic alignment by projecting an alignment beam toward the cornea and receiving reflected light thereof, which is disclosed in Japanese Patent Application Laid-Open No. 62-19150, the ophthalmic apparatus arranged to perform such control as to retract an eye examination unit when the eye examination unit is too close to an eye to be examined, using an alignment optical system and a measurement optical system for positioning between the eye to be examined and the apparatus, an apparatus arranged to carry out anti-proximity control of the eye examination unit by use of an ultrasonic sensor or a capacitance sensor placed on the eye side of the eye examination unit, an apparatus with a driving unit preliminarily so limited as to prevent the eye examination unit from approaching the eye over a predetermined distance, and so on.
In the above-stated prior art examples, however, where the automatic alignment and anti-proximity is carried out by use of the alignment optical system, a light receiving unit cannot receive the cornea-reflected light unless the examination unit is preliminarily positioned to some extent vertically and laterally with respect to the eye to be examined; the detection range of the automatic alignment and anti-proximity becomes narrower thereby. When the ultrasonic sensor or the capacitance sensor is used, the structure becomes complicated because of increase of components including those for mounting of these sensors, a driving circuit, a detection circuit, and so on. When the driving unit is limited to the predetermined position, there arises a problem that the eye to be detected cannot be detected if the eye suddenly approaches the apparatus immediately before eye examination.
An object of the present invention is to provide an ophthalmic apparatus of safe and simple structure capable of widening the detection range of automatic alignment and carrying out the anti-proximity in a wide range, overcoming the above problems.
An ophthalmic apparatus of the present invention is an ophthalmic apparatus comprising:
a measurement unit for measuring an eye to be examined;
an illumination light source disposed near the measurement unit, for illuminating the eye;
an area sensor for picking up an image of the eye illuminated by said illumination light source;
driving means for driving said measurement unit relative to the eye forward or backward;
determining means for determining whether signal levels throughout an entire area of said area sensor are not more than a predetermined level; and
control means for controlling said driving means so as to drive the measurement unit away from said eye, when said determining means determines that the signal levels are not more than the predetermined level.
Another ophthalmic apparatus of the present invention is an ophthalmic apparatus comprising:
a measurement unit for measuring an eye to be examined;
an illumination light source disposed near the measurement unit, for illuminating the eye;
an area sensor for picking up an image of the anterior part of the eye illuminated by said illumination light source;
an optical unit for optically splitting the image of the anterior part of the eye and for projecting the images of the anterior part of the eye thus split onto said area sensor;
driving means for driving said measurement unit relative to the eye forward or backward;
detecting means for detecting a deviation amount between the images of the pupil split by said optical unit, based on an output of said area sensor; and
control means for controlling said driving means so as to drive the measurement unit away from said eye, based on the result of detection by said detecting means.
Still another ophthalmic apparatus of the present invention is an ophthalmic apparatus comprising:
a measurement unit for measuring an eye to be examined;
an illumination light source disposed near the measurement unit, for illuminating the eye;
an area sensor for picking up an image of the anterior part of the eye illuminated by said illumination light source;
driving means for driving said measurement unit relative to the eye forward or backward;
determining means for determining a size of the pupil of the eye, based on an output of said area sensor; and
control means for controlling said driving means so as to drive the measurement unit away from said eye, based on the result of determination by said determining means.